The only times I use omnis or wide cardioids is when the acoustical environment is damn near perfect to begin with, and when the sound balance at the recording position is optimal, or I can even go a little closer and pick up a bit of extra detail beyond what the audience would hear. You know--those rare and blessed situations in which the recording essentially makes itself.
When that miracle occurs, these more open patterns are my favorite way to take advantage of it. The results are just so easy and pleasant to listen to. And to me, one of the fun things about using them in that type of situation is the amount of detail they can pick up while still keeping that innocent quality; it's like having your cake and eating it, too.
But it all depends on acoustical and logistical factors that rarely line up so neatly, even though I'm almost always the official sound engineer for anything I record (e.g. when the concert producers don't want microphones to be seen where I would like to put them). So for all less-than-perfect situations, which is well over 90% of the time, I use capsules with higher directivity.
--best regards